CA1181550A - Process for producing foamable polyolefin particles - Google Patents
Process for producing foamable polyolefin particlesInfo
- Publication number
- CA1181550A CA1181550A CA000428154A CA428154A CA1181550A CA 1181550 A CA1181550 A CA 1181550A CA 000428154 A CA000428154 A CA 000428154A CA 428154 A CA428154 A CA 428154A CA 1181550 A CA1181550 A CA 1181550A
- Authority
- CA
- Canada
- Prior art keywords
- particles
- polyolefin
- weight
- parts
- polyolefin particles
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/16—Making expandable particles
- C08J9/18—Making expandable particles by impregnating polymer particles with the blowing agent
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
- C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
- C08J9/14—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent organic
- C08J9/141—Hydrocarbons
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2351/00—Characterised by the use of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S264/00—Plastic and nonmetallic article shaping or treating: processes
- Y10S264/05—Use of one or more blowing agents together
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S521/00—Synthetic resins or natural rubbers -- part of the class 520 series
- Y10S521/91—Plural blowing agents for producing nonpolyurethane cellular products
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention is directed to a process for producing foamable polyolefin particles comprising adding a mixture of 3 to 15 parts by weight of a blowing agent and 0.5 to 5 parts by weight of a blowing aid to 100 parts by weight of poly-olefin particles maintained in a fluid state. The addition of the mixture of blowing agent and blowing aid is conducted under substantially anhydrous conditions, which result in the blowing agent being present in the particles in a gas phase and not a liquid phase. Polyolefin particles comprise polyolefin resin with vinylaromatic resin chemically bonded thereto.
The present invention is directed to a process for producing foamable polyolefin particles comprising adding a mixture of 3 to 15 parts by weight of a blowing agent and 0.5 to 5 parts by weight of a blowing aid to 100 parts by weight of poly-olefin particles maintained in a fluid state. The addition of the mixture of blowing agent and blowing aid is conducted under substantially anhydrous conditions, which result in the blowing agent being present in the particles in a gas phase and not a liquid phase. Polyolefin particles comprise polyolefin resin with vinylaromatic resin chemically bonded thereto.
Description
PROCESS FOR PRODUCING FOAMABLE
POLYOLEFIN PARTICLES
The present invention is directed to a process for pro-ducing foamable polyolefin particles and, more particularly, to a process for producing foam~ble polyalefin. particles which can maintain an excellent foaming ability over a long period of time, which are capable of forming uniform cells, ancl which can be impregnated with a dye at a high impregnation effic ency and a good coloration state without uneven dyeing.
BACKGROUND OF THE INVENTION
Prscesses for impregnating a blowing agent, such as pro- -pane, butane or pentane, into polyolefin particles composed of ; polyolefin resin with at least a part o~ a vinylaromatic resin chemically bound thereto are described in US Patents 3,959,189 and 4,168,353. In these processes, the impregnation of the blowing agent is prepared by a step of providing a suspension o the polyolefin particles, a step of washing the particles with water, and a subsequent dehydrating step for removing a suspension stabilizer deposited on the surface of resulting foamable polyo-lefin particles after completion of the impregnation. Since these water washing and dehydrating steps are conducted under normal pressures, part of the impregnated blowing agent escapes during these steps, which results in a reduction in the expansion ratio o the resulting impregnated particles.
o 1 In colored foamable polyolefin particles prepared by addition of a dye or the like, defects have been encountered in that the efficiency of impregnating the dye is poor and in tha~
washing of an impregnation vessel is necessary after completion of the impregnation, d~e to adhesion of the dye onto ~he walls of the vessel SU~ARY OF THE INVENTION
The present invention overcomes the above-described defects in the prior art, and provides a process for producing foamable polyolefin particles which does not require the steps of water washing and dehydration of resulting foamaDle poly-olefin particles, after completion of impregnation of a blowing agent therein. Also, the present invention provides a process for preparing colored foamable polyolefin particles, wherein a - dye is impregnated into the particles with a good impregnation efficiency. Namely, the present invention includes a process for producing foamable polyolefin particles which comprises adding, to 100 parts by weight of fluid-state polyolefin par~icles composed of polyolefin resin with at least part of a vinylaroma~ic resin chemically bound thereto, 3 to15 parts by weight of a blow~
ing agent and 0.5 to 5 parts by weight of a blowing aid under substantially anhydrous atmosphere to impregnate the blowing agent and the blowing aid in the particles so that the blowing `agent and the blowing aid exist in the particle in gas phase and not in liquid phase.
DETAILED DESCRIPTION OF THE INVENTION
The polyolefin particles used in the present inven~ior are composed of polyolefin resin with at least part of a vinyl-aromatic resin chemically bound thereto. The phrase at lea~
POLYOLEFIN PARTICLES
The present invention is directed to a process for pro-ducing foamable polyolefin particles and, more particularly, to a process for producing foam~ble polyalefin. particles which can maintain an excellent foaming ability over a long period of time, which are capable of forming uniform cells, ancl which can be impregnated with a dye at a high impregnation effic ency and a good coloration state without uneven dyeing.
BACKGROUND OF THE INVENTION
Prscesses for impregnating a blowing agent, such as pro- -pane, butane or pentane, into polyolefin particles composed of ; polyolefin resin with at least a part o~ a vinylaromatic resin chemically bound thereto are described in US Patents 3,959,189 and 4,168,353. In these processes, the impregnation of the blowing agent is prepared by a step of providing a suspension o the polyolefin particles, a step of washing the particles with water, and a subsequent dehydrating step for removing a suspension stabilizer deposited on the surface of resulting foamable polyo-lefin particles after completion of the impregnation. Since these water washing and dehydrating steps are conducted under normal pressures, part of the impregnated blowing agent escapes during these steps, which results in a reduction in the expansion ratio o the resulting impregnated particles.
o 1 In colored foamable polyolefin particles prepared by addition of a dye or the like, defects have been encountered in that the efficiency of impregnating the dye is poor and in tha~
washing of an impregnation vessel is necessary after completion of the impregnation, d~e to adhesion of the dye onto ~he walls of the vessel SU~ARY OF THE INVENTION
The present invention overcomes the above-described defects in the prior art, and provides a process for producing foamable polyolefin particles which does not require the steps of water washing and dehydration of resulting foamaDle poly-olefin particles, after completion of impregnation of a blowing agent therein. Also, the present invention provides a process for preparing colored foamable polyolefin particles, wherein a - dye is impregnated into the particles with a good impregnation efficiency. Namely, the present invention includes a process for producing foamable polyolefin particles which comprises adding, to 100 parts by weight of fluid-state polyolefin par~icles composed of polyolefin resin with at least part of a vinylaroma~ic resin chemically bound thereto, 3 to15 parts by weight of a blow~
ing agent and 0.5 to 5 parts by weight of a blowing aid under substantially anhydrous atmosphere to impregnate the blowing agent and the blowing aid in the particles so that the blowing `agent and the blowing aid exist in the particle in gas phase and not in liquid phase.
DETAILED DESCRIPTION OF THE INVENTION
The polyolefin particles used in the present inven~ior are composed of polyolefin resin with at least part of a vinyl-aromatic resin chemically bound thereto. The phrase at lea~
(2) ~. .
s~
1 part of a vinylaromatic resin "chemically bound thereto" means that at least part of the polyolefin resin molecular chains are grafted and/or cross-linked with vinylaromatic resin.
Such polyolefin particles can be obtainted by processes described in U.S. Patents 3,959,189 and 4,168,353 which comprise suspending polyolefin resin and vinylaromatic monomer in an aqueous suspension and polymerizing the monomer onto the resin.
The polyolefin resins to be used in the present inven~
tion include ethylene homopolymers, propylene homopolymers, and ethylene copolymers having an ethylene in a content of 50% or more by weight, such as an ethylene-vinyl acetate copolymer, and ethylene-butyl acrylate copolymer, and ethylene-methyl methcryla~e copolymer.
The vinylaromatic resins to be chemically bound at least in part to the polyolefin resin include polystyrene, polymethyl-styrene, polyhalogenated styrene, and styrene copolymers having a styrene in a con~ent of 50 wt % or more, such as a styrene-divinylbenzene copolymer and a styrene-methyl methacrylate copolymer.
The ratio of the above-described polyolefin resin to vinylaromatic resin used is, preferably, 20 to 70 wt % of the polyolefin resin and 80 to 30 wt % of the vinylaromatic rPsin.
If the amount of the polyolefin resin used is less than 20 wt %, rigidity of a resulting molding becomes too strong, thereby resulting in an unsuitable cushioning material. On the other hand, if the amount of the polyolefin resin used exceeds 70 wt %, the blowing agent contained in the foamable polyolefin particles escapes very fast, and foamed moldings with a low bulk density are difficult to obtain.
(33 55~
l In the present inventlon, the polyolefin resin is used in the form of pellets or globular particles.
A blowing agent is used for rendering the polyolefin particles foamable. The blowing agents used have the property that they do not dissolve or only slightly swell th~ polyolefin resin and the vinylaromatic resin formed on the polyolefin resin particles. Further, the blowing agents should have a boiling point lower than the softening point of the polyolefin resin and should be gaseous or liquid at room temp-erature (about 20 to 30 C) and normal pressure (about atmospheric).These blowing agents are well known in the art and generally have boiling points ranging from -42C to 80C, more generally -1~C
to 36C. Suitable blowing agents include aliphatic hydrocarbons such as n-propane, n-butane, iso-butane, n-pentane, iso-pentane, n-hexane and neopentane; cycloaliphatic hydrocarbons, such as cyclobutane and cyclopentane; and halogenated hydrocarbons, such as methyl chloride, ethyl chloride, methylene chloride, trichloro-fluoromethane, dichlorofluoromethane, dichlorodifluoromethane, chlorodifluoromethane, and dichlorotetrafluoroethane, etc. These blowing agents can be used alone or as mixtures of two or more thereof. The preferable amount of the blowing agent is in a range of about 3 to 15 % by weight based on the weight of the formed polyolefin resin particles. Of the above-described blow~
ing agents, n-butane and n-pentane are~ preferably used in the present invention.
In the present invention the above-described blowing agent is used in combination with a blowing aid. This blowing aid causes the interior of the particles to be in a plastic state, thereby facilitating the foaming of the particles. ~nen foamabJe particles are heated, the expansion ratio reaches a maximu~ level after a certain period of time.
(4) ." .
1 The bLowing aid is used to control ~he time necessary for the particles to reach the maximum expansion ratio, so as to be within range of 2 to 10 minutes, preferably 3 to 6 minutes.
The use of the blowing aid facilitates pre-foaming prccedure and saves energy. In addition, the surface state of resulting mold ings and welding sf particles is remarkably improved by the use of ~he blowing aid, when compared to processes wher~ it is not used.
The blowing aid is used for the purpose of foaming the foa~able polyolefin particles in a short period of time at a high expansion ratio. Blowing aids which are miscible with the part-icles can be used in the present invention.
Representative blowing aids are compounds, which have a boiling point of about 80C to about 150C, such as benzene, toluene, xylene, trichlene, perchlene, cyclohexane, carbon tetrachloride, styrene monomer, etc.
This blowing aid is used in an amount of 0.5 to 5 par~s by weight per 100 parts by weight of the polyolefin particles.
This blowing agent and the blowing aid are added to poly-olefi.n particles in a fluid state under a substantially anhydrousatmosphere. The phrase "under a substantially anhydrous atmos-phere" means that aqueous mediums, such as a suspension, are not used, which is different from the types of processes of adding the blowing agent and the blowing aid to polyolefin part:L-cles suspended in an aqueous suspension.
In the present invention, the blowing agent must be impregnated in the polyolefin particles in a gas phase. That ~is, if th~ impregnation procedure is conducted in a liquid phase, the following defects result. Of the above-described blowing agents, those which exert a comparatively strong swelling e~fec~
(5) 1 on polyolefin particles, such as n-pentane and iso-pentane, fail to provide ~oamable polyolefin particles having uniform cells due to the difference in impregnation rate between a blowing agent portion in liquid phase and a blowing agent portion in ~as phase. Further, the ployolefin particles in contact with the blowing agent portion in liquid phase bond to each other, because the particle surface is attacked by the liquid phase blowing agent portion.
Accordingly, in the present invention when usiny such blowing 10 agents, they must be quantitatively added so as not to form a liquid phase portion. On the other hand, when using those blowing agents which are low-boiling compounds and which exert a compar-atively weak swelling effect on polyolefin particles, such as n-propane and n-butane, these may be added all at once. This is because they are impregnated in polyolefin particles so fast that they are absorbed in a short period of time and are converted from liquid phase to gas phase in a sufficiently short period of time. As a result, impregnation is effected in the gas phase without allowing a liquid phase portion to exist after completion 20 of the impregnation, thereby providing foamable polyolefin part~
icles having uniform cells and being free of any bonding bet-ween the particles.
During the addition of the blowing agent and the blowing aid to the polyolefin particles according to the present invention, the polyolefin particles must be in a fluid state. This fluid state is a state wherein polyolefin particles are not at rest. In order to keep the polyolefin particles in the fluid state, rotary vessels such as a V-blender or a tumbler are used at 10 to 30 rpm. It .i5 possible to provide the fluid state by stirring using a stirrer, (6) 5~ ~
l ho~ever, stirring polyolefin particles in an anhydrous sta~e requires a large amount of pow~r; and therefore, this is not preferred. In the present invention, a pressure-resistant vessel is used for conducting the gas phase impregnation As described heretofore, addition of the blowing agent and the blowing aid to fluid-state polyolefin particles is con-ducted quantitatively or all at once depending upon the type of the blowing agent used. In conducting the quantitative addition;
the blowing agent is added dropwise at a rate controlled so tha~
the addition is completed in about 5 to about 180 rninutes. By this controlling of the addition of the blowing agents a foamable polyolefin particle can be obtained; which, upon foaming, does not undergo coarsening of cells, form uneven cells or bond the particles to each other.
If the time for adding the blowing agent exceeds 180 minutes, the cells undergo no further change; thus extending the adding time is economically disadvantageous.
In the present invention, the blowing agent and the blowing aid are used in a mixture. The use of the mixture of the blowing agent and the blowing aid provides particles having uniform cells.
In the present invention, the polyolefin particles are placed in a vessel equipped with a rotating mechanism, and the blowing agent and the blowing aid are added thereto while the particles are brought into a fluid state in a vessel being rotated by means of the rotating mechanism. After completion of, or during this addition, the contents of the vessel are maintained or heated to a tempe ature of from ordinary or room temperat~lre to 70C, preferably, to about 50 to 60C. After raising the temperature, the contents are maintained at the same temper~ture for a given period of time, then cooled to ordinary temperatureC99 followed by removing the foamable product.
. (7) 1 When n-butane and toluene are used as the blowing agent and a blowing aid, respectively, and the contents are k4pt at ternperatures of 50 to 55C, about 2 hours are sufficient for heating the contents to 50 to 55C and cooling to ordinary temperatures. When n-pentane and toluene are used as a blowing agent and a blowing aid, respectively, about 3 hours are sufficient for heating to 50 to 55C, after dropwise addition in 40 to 60 minutes, and cooling to ordinary tem-peratures.
When n-pentane is used as a blowing agent, it is preferably used in an amount ranging from 7.0 to 12.5, pre-ferably 9.5 to 10.5, parts by weight based on the weight of polyolefin particles. If the amount exceeds 12.5 par~s by weight, the resulting foamable polyolefin particles undergo, ~ upon foa~.ing, coarsening of formed cells and destruction of cell walls. On the other hand, if less than 7.0 parts by ,, ., .~
weight, a sufficient expansion ratio cannot be attained.
By applying a dye onto polyolefin particle surfac~s before addition of the blowing agent and the blowing aid, or by dissolving a dye in the blowing agent or the blowing aid and adding the resulting solution to the particles; the process of the present invention advantageously provides foamable polyolefin particles which are beautifully colored in a good coloration state with no uneven coloration and which have a high impregnation efficiency of dye.
As the dye used for obtaining dyed foaming polyolefin particles, various known dyes such as monoazo dyes~ diazo dye~
anthraquinone dyes, etc., are employable. In order to obtain the .
(~) 1 dyed foa~ing polyolefin particles, predeter~ined amounts of polyolefin particles which are used in the present invention are first charged into a vessel. Thereafter, a predetermined amount of the dye and a small amount of a blowing agen~ are charged into the sealed vessel, whereby the dye and blowing agent.
are stirred and mixed with the polyolefill particles. The stirring and mixing of the dye and blowing agent with the polyolefin particles can be conducted either individually or simultaneously.
~n general, the dye is preliminarily added to th~ polyolefin p ~ icles charged into the sealed vessel to thereby s~ir and mix therewithO T~s causes the dye tocover or adhere to the surfaces of the par~icles.
Then, a small amount of the blowing agent is gradually added thereto by, for example, dropwise addition, to thereby thoroughly effect the stirring and mixing. After the dye has been uniformly adhered to the surfaces of the polyolefin particles, the residual amount of the blowing agent !and a predetermined amount of a blowing aid are added thereto.
In the present invention, since the blowing agent and blowing aid are impregnated into the polyolefin particles within 2Q a shor~ period of time, it is necessary to select dyes which can be impregnated within a short period o~ time. For such purposes, it is preferred to use those having a small molecular weight and a solvation effect against the polyolefin particles.
The amount of the dye to be added may be-comparatively small in comparison with the amount of polyolefin particles and usually is 0.005 to 1.0 parts by weight, based on 100 parts by weight of the particles, with 0.03 to 0.6 parts by weight being preferred ~ the amount is too high, an excess amount of the dye remains9 and therefore, such is not preferred.
Flame retardants such as tris(2,3-dibromopropyl)phosphate9 hexabromododecane, tribromophenyl allyl ether, etc., antiblocking (9) l agents for pre-foaming such as ethylenebisamide, antistatic agents such as polyethylene glycol, etc. may be used in the present invention.
The foamable polyolefin particles obtalned by the present invention possess an excellent foaming ability over a long period of time.
In other words the foamable polyolefin obtained from the present invention have a long shelf life, in that they can be foamed a long period of time after their production and still provide a foam containing uniform cells. Thus, th~ ~oamable polyolefin particles of the present invention are extremely advantageous in view of storage and transportation, when compared to conventional foamable polyolefin particles. In particular, when stored at low temperatures of about 10C, the foamable polyolefin particles obtained by the present invention do not undergo any change in thelr foaming ability and moldability for 2 to 3 weeksO
In addition, colored foamable polyolefin particles obtained by using a dye in accordance with the present invention are uni-formly colored to the core.
The present invention will now be described in more de~ail by reference to the follwoing examples which, however, are not to be construed as limiting the present invention in any way.
Example l l,500 Parts by weight of polyolefin particles, obtained by subjecting 40 % by weight of polyethylene and 60 ~ by weight of styrene monomer to polymerization conditions in an aqueous medium, were placed in a cylindrical vessel (250 mm x 180~mm) equipped with a porous screen through which the particles can not (10) l pass,but through which a blowing agent gas can pass; then the particles above the screen were uniformly stirred by a stirring blade.
A mixture solution of 225 parts by weight of pentane and 30 parts by weight of toluene was introduced into -thc vessel under the screen in about 5 minutes, while the particles were main-tained in fluid state; thereafter impregnation was conducted for 3 hours while keeping the temperature at 35 C.
This impregnating procedure was carried out with the vessel tightly closed. After 3 hours of impregnation, the amount of the mixture of pentane and toluene absorbed by the particles was measured immediately after taking the particles out of the vessel and found to be 196 parts by weight.
The thus-obtained foamable polyolefin particles were allowed to stand in the atmosphere for a given period of time; they were then heated by introducing a 0.2 kg/cm2 steam into a foaming vessel (about 0.4 m3) to obtain foams; and thereafter, the expansion multiple and the cell state were measured. Further,the charac-teristics of pentane and toluene absorption and migration into the ~0 interior of the resln particles was determined in terms of the size of the core (non-impregnated) formed in the center of the parti-cles. The results thus obtained are shown in T~ble l.
Table l Standing Expansion State of Presence Time Multi~le Cells _ of Core Immediately after 38 130sec)*l good*2 no cores removal 2 hrs. 36 (30sec) good no cores 4 hrs. 38 ~60sec) good no cores 12 hrs. 30 (60sec) good no cores ~11) 1 *1. The time given in parentheses is the time or introducing steam.
*2 The rating "good" means uniform and fine foamed cells having a definite shape.
Example 2 A foam was prepared in the same manner as in Example l except for changing the amount of pentane to 165 parts, using 37 parts by weight of cyclohexane in place of toluene, and changing the impregnation conditions to 50C in impregnating temperature and 2 hours in impregnating time. The amoun~ of a mixture of pentane and toluene absorbed was measured after the 2-hr impregnation procedure The absorption amount wasfound ~o be 181 parts by weight immediately after removing the impregna-tion product. Foaming properties versus standing time were also evaluated in the same manner as in Example 1. The results thus obtained are tabulated in Table 2. --Table 2 Standing Expansion State of Presence Time Multiple Cells of Cores Immediately 35 (30 sec) good no cores after removal 2 hrs. 33 ~30 sec) good no cores 4 hrs. 37 (60 sec) good no cores 12 hrs. 2~ (60 sec) good no cores Example 3
s~
1 part of a vinylaromatic resin "chemically bound thereto" means that at least part of the polyolefin resin molecular chains are grafted and/or cross-linked with vinylaromatic resin.
Such polyolefin particles can be obtainted by processes described in U.S. Patents 3,959,189 and 4,168,353 which comprise suspending polyolefin resin and vinylaromatic monomer in an aqueous suspension and polymerizing the monomer onto the resin.
The polyolefin resins to be used in the present inven~
tion include ethylene homopolymers, propylene homopolymers, and ethylene copolymers having an ethylene in a content of 50% or more by weight, such as an ethylene-vinyl acetate copolymer, and ethylene-butyl acrylate copolymer, and ethylene-methyl methcryla~e copolymer.
The vinylaromatic resins to be chemically bound at least in part to the polyolefin resin include polystyrene, polymethyl-styrene, polyhalogenated styrene, and styrene copolymers having a styrene in a con~ent of 50 wt % or more, such as a styrene-divinylbenzene copolymer and a styrene-methyl methacrylate copolymer.
The ratio of the above-described polyolefin resin to vinylaromatic resin used is, preferably, 20 to 70 wt % of the polyolefin resin and 80 to 30 wt % of the vinylaromatic rPsin.
If the amount of the polyolefin resin used is less than 20 wt %, rigidity of a resulting molding becomes too strong, thereby resulting in an unsuitable cushioning material. On the other hand, if the amount of the polyolefin resin used exceeds 70 wt %, the blowing agent contained in the foamable polyolefin particles escapes very fast, and foamed moldings with a low bulk density are difficult to obtain.
(33 55~
l In the present inventlon, the polyolefin resin is used in the form of pellets or globular particles.
A blowing agent is used for rendering the polyolefin particles foamable. The blowing agents used have the property that they do not dissolve or only slightly swell th~ polyolefin resin and the vinylaromatic resin formed on the polyolefin resin particles. Further, the blowing agents should have a boiling point lower than the softening point of the polyolefin resin and should be gaseous or liquid at room temp-erature (about 20 to 30 C) and normal pressure (about atmospheric).These blowing agents are well known in the art and generally have boiling points ranging from -42C to 80C, more generally -1~C
to 36C. Suitable blowing agents include aliphatic hydrocarbons such as n-propane, n-butane, iso-butane, n-pentane, iso-pentane, n-hexane and neopentane; cycloaliphatic hydrocarbons, such as cyclobutane and cyclopentane; and halogenated hydrocarbons, such as methyl chloride, ethyl chloride, methylene chloride, trichloro-fluoromethane, dichlorofluoromethane, dichlorodifluoromethane, chlorodifluoromethane, and dichlorotetrafluoroethane, etc. These blowing agents can be used alone or as mixtures of two or more thereof. The preferable amount of the blowing agent is in a range of about 3 to 15 % by weight based on the weight of the formed polyolefin resin particles. Of the above-described blow~
ing agents, n-butane and n-pentane are~ preferably used in the present invention.
In the present invention the above-described blowing agent is used in combination with a blowing aid. This blowing aid causes the interior of the particles to be in a plastic state, thereby facilitating the foaming of the particles. ~nen foamabJe particles are heated, the expansion ratio reaches a maximu~ level after a certain period of time.
(4) ." .
1 The bLowing aid is used to control ~he time necessary for the particles to reach the maximum expansion ratio, so as to be within range of 2 to 10 minutes, preferably 3 to 6 minutes.
The use of the blowing aid facilitates pre-foaming prccedure and saves energy. In addition, the surface state of resulting mold ings and welding sf particles is remarkably improved by the use of ~he blowing aid, when compared to processes wher~ it is not used.
The blowing aid is used for the purpose of foaming the foa~able polyolefin particles in a short period of time at a high expansion ratio. Blowing aids which are miscible with the part-icles can be used in the present invention.
Representative blowing aids are compounds, which have a boiling point of about 80C to about 150C, such as benzene, toluene, xylene, trichlene, perchlene, cyclohexane, carbon tetrachloride, styrene monomer, etc.
This blowing aid is used in an amount of 0.5 to 5 par~s by weight per 100 parts by weight of the polyolefin particles.
This blowing agent and the blowing aid are added to poly-olefi.n particles in a fluid state under a substantially anhydrousatmosphere. The phrase "under a substantially anhydrous atmos-phere" means that aqueous mediums, such as a suspension, are not used, which is different from the types of processes of adding the blowing agent and the blowing aid to polyolefin part:L-cles suspended in an aqueous suspension.
In the present invention, the blowing agent must be impregnated in the polyolefin particles in a gas phase. That ~is, if th~ impregnation procedure is conducted in a liquid phase, the following defects result. Of the above-described blowing agents, those which exert a comparatively strong swelling e~fec~
(5) 1 on polyolefin particles, such as n-pentane and iso-pentane, fail to provide ~oamable polyolefin particles having uniform cells due to the difference in impregnation rate between a blowing agent portion in liquid phase and a blowing agent portion in ~as phase. Further, the ployolefin particles in contact with the blowing agent portion in liquid phase bond to each other, because the particle surface is attacked by the liquid phase blowing agent portion.
Accordingly, in the present invention when usiny such blowing 10 agents, they must be quantitatively added so as not to form a liquid phase portion. On the other hand, when using those blowing agents which are low-boiling compounds and which exert a compar-atively weak swelling effect on polyolefin particles, such as n-propane and n-butane, these may be added all at once. This is because they are impregnated in polyolefin particles so fast that they are absorbed in a short period of time and are converted from liquid phase to gas phase in a sufficiently short period of time. As a result, impregnation is effected in the gas phase without allowing a liquid phase portion to exist after completion 20 of the impregnation, thereby providing foamable polyolefin part~
icles having uniform cells and being free of any bonding bet-ween the particles.
During the addition of the blowing agent and the blowing aid to the polyolefin particles according to the present invention, the polyolefin particles must be in a fluid state. This fluid state is a state wherein polyolefin particles are not at rest. In order to keep the polyolefin particles in the fluid state, rotary vessels such as a V-blender or a tumbler are used at 10 to 30 rpm. It .i5 possible to provide the fluid state by stirring using a stirrer, (6) 5~ ~
l ho~ever, stirring polyolefin particles in an anhydrous sta~e requires a large amount of pow~r; and therefore, this is not preferred. In the present invention, a pressure-resistant vessel is used for conducting the gas phase impregnation As described heretofore, addition of the blowing agent and the blowing aid to fluid-state polyolefin particles is con-ducted quantitatively or all at once depending upon the type of the blowing agent used. In conducting the quantitative addition;
the blowing agent is added dropwise at a rate controlled so tha~
the addition is completed in about 5 to about 180 rninutes. By this controlling of the addition of the blowing agents a foamable polyolefin particle can be obtained; which, upon foaming, does not undergo coarsening of cells, form uneven cells or bond the particles to each other.
If the time for adding the blowing agent exceeds 180 minutes, the cells undergo no further change; thus extending the adding time is economically disadvantageous.
In the present invention, the blowing agent and the blowing aid are used in a mixture. The use of the mixture of the blowing agent and the blowing aid provides particles having uniform cells.
In the present invention, the polyolefin particles are placed in a vessel equipped with a rotating mechanism, and the blowing agent and the blowing aid are added thereto while the particles are brought into a fluid state in a vessel being rotated by means of the rotating mechanism. After completion of, or during this addition, the contents of the vessel are maintained or heated to a tempe ature of from ordinary or room temperat~lre to 70C, preferably, to about 50 to 60C. After raising the temperature, the contents are maintained at the same temper~ture for a given period of time, then cooled to ordinary temperatureC99 followed by removing the foamable product.
. (7) 1 When n-butane and toluene are used as the blowing agent and a blowing aid, respectively, and the contents are k4pt at ternperatures of 50 to 55C, about 2 hours are sufficient for heating the contents to 50 to 55C and cooling to ordinary temperatures. When n-pentane and toluene are used as a blowing agent and a blowing aid, respectively, about 3 hours are sufficient for heating to 50 to 55C, after dropwise addition in 40 to 60 minutes, and cooling to ordinary tem-peratures.
When n-pentane is used as a blowing agent, it is preferably used in an amount ranging from 7.0 to 12.5, pre-ferably 9.5 to 10.5, parts by weight based on the weight of polyolefin particles. If the amount exceeds 12.5 par~s by weight, the resulting foamable polyolefin particles undergo, ~ upon foa~.ing, coarsening of formed cells and destruction of cell walls. On the other hand, if less than 7.0 parts by ,, ., .~
weight, a sufficient expansion ratio cannot be attained.
By applying a dye onto polyolefin particle surfac~s before addition of the blowing agent and the blowing aid, or by dissolving a dye in the blowing agent or the blowing aid and adding the resulting solution to the particles; the process of the present invention advantageously provides foamable polyolefin particles which are beautifully colored in a good coloration state with no uneven coloration and which have a high impregnation efficiency of dye.
As the dye used for obtaining dyed foaming polyolefin particles, various known dyes such as monoazo dyes~ diazo dye~
anthraquinone dyes, etc., are employable. In order to obtain the .
(~) 1 dyed foa~ing polyolefin particles, predeter~ined amounts of polyolefin particles which are used in the present invention are first charged into a vessel. Thereafter, a predetermined amount of the dye and a small amount of a blowing agen~ are charged into the sealed vessel, whereby the dye and blowing agent.
are stirred and mixed with the polyolefill particles. The stirring and mixing of the dye and blowing agent with the polyolefin particles can be conducted either individually or simultaneously.
~n general, the dye is preliminarily added to th~ polyolefin p ~ icles charged into the sealed vessel to thereby s~ir and mix therewithO T~s causes the dye tocover or adhere to the surfaces of the par~icles.
Then, a small amount of the blowing agent is gradually added thereto by, for example, dropwise addition, to thereby thoroughly effect the stirring and mixing. After the dye has been uniformly adhered to the surfaces of the polyolefin particles, the residual amount of the blowing agent !and a predetermined amount of a blowing aid are added thereto.
In the present invention, since the blowing agent and blowing aid are impregnated into the polyolefin particles within 2Q a shor~ period of time, it is necessary to select dyes which can be impregnated within a short period o~ time. For such purposes, it is preferred to use those having a small molecular weight and a solvation effect against the polyolefin particles.
The amount of the dye to be added may be-comparatively small in comparison with the amount of polyolefin particles and usually is 0.005 to 1.0 parts by weight, based on 100 parts by weight of the particles, with 0.03 to 0.6 parts by weight being preferred ~ the amount is too high, an excess amount of the dye remains9 and therefore, such is not preferred.
Flame retardants such as tris(2,3-dibromopropyl)phosphate9 hexabromododecane, tribromophenyl allyl ether, etc., antiblocking (9) l agents for pre-foaming such as ethylenebisamide, antistatic agents such as polyethylene glycol, etc. may be used in the present invention.
The foamable polyolefin particles obtalned by the present invention possess an excellent foaming ability over a long period of time.
In other words the foamable polyolefin obtained from the present invention have a long shelf life, in that they can be foamed a long period of time after their production and still provide a foam containing uniform cells. Thus, th~ ~oamable polyolefin particles of the present invention are extremely advantageous in view of storage and transportation, when compared to conventional foamable polyolefin particles. In particular, when stored at low temperatures of about 10C, the foamable polyolefin particles obtained by the present invention do not undergo any change in thelr foaming ability and moldability for 2 to 3 weeksO
In addition, colored foamable polyolefin particles obtained by using a dye in accordance with the present invention are uni-formly colored to the core.
The present invention will now be described in more de~ail by reference to the follwoing examples which, however, are not to be construed as limiting the present invention in any way.
Example l l,500 Parts by weight of polyolefin particles, obtained by subjecting 40 % by weight of polyethylene and 60 ~ by weight of styrene monomer to polymerization conditions in an aqueous medium, were placed in a cylindrical vessel (250 mm x 180~mm) equipped with a porous screen through which the particles can not (10) l pass,but through which a blowing agent gas can pass; then the particles above the screen were uniformly stirred by a stirring blade.
A mixture solution of 225 parts by weight of pentane and 30 parts by weight of toluene was introduced into -thc vessel under the screen in about 5 minutes, while the particles were main-tained in fluid state; thereafter impregnation was conducted for 3 hours while keeping the temperature at 35 C.
This impregnating procedure was carried out with the vessel tightly closed. After 3 hours of impregnation, the amount of the mixture of pentane and toluene absorbed by the particles was measured immediately after taking the particles out of the vessel and found to be 196 parts by weight.
The thus-obtained foamable polyolefin particles were allowed to stand in the atmosphere for a given period of time; they were then heated by introducing a 0.2 kg/cm2 steam into a foaming vessel (about 0.4 m3) to obtain foams; and thereafter, the expansion multiple and the cell state were measured. Further,the charac-teristics of pentane and toluene absorption and migration into the ~0 interior of the resln particles was determined in terms of the size of the core (non-impregnated) formed in the center of the parti-cles. The results thus obtained are shown in T~ble l.
Table l Standing Expansion State of Presence Time Multi~le Cells _ of Core Immediately after 38 130sec)*l good*2 no cores removal 2 hrs. 36 (30sec) good no cores 4 hrs. 38 ~60sec) good no cores 12 hrs. 30 (60sec) good no cores ~11) 1 *1. The time given in parentheses is the time or introducing steam.
*2 The rating "good" means uniform and fine foamed cells having a definite shape.
Example 2 A foam was prepared in the same manner as in Example l except for changing the amount of pentane to 165 parts, using 37 parts by weight of cyclohexane in place of toluene, and changing the impregnation conditions to 50C in impregnating temperature and 2 hours in impregnating time. The amoun~ of a mixture of pentane and toluene absorbed was measured after the 2-hr impregnation procedure The absorption amount wasfound ~o be 181 parts by weight immediately after removing the impregna-tion product. Foaming properties versus standing time were also evaluated in the same manner as in Example 1. The results thus obtained are tabulated in Table 2. --Table 2 Standing Expansion State of Presence Time Multiple Cells of Cores Immediately 35 (30 sec) good no cores after removal 2 hrs. 33 ~30 sec) good no cores 4 hrs. 37 (60 sec) good no cores 12 hrs. 2~ (60 sec) good no cores Example 3
3,000 Parts by weight of polyolefin particles 9 ob~a.Jnedby subjecting 50 % by weight of polyethylen~ and 50 % by weight (12) 1 of styrene monomer to polymerization conditions in an aqueous medium, was placed in a rotary vessel, and a mixture of 450 parts by welght of pentane and 40 parts by weight of toluene was added into the vessel through the shaft in the vessel.
Upon this addition, the rotary vessel and the resin were maintained at 35C and the adding rate was adjusted so that the total amount of the mlxture could be added in three hours.
The amount of the mixture solution absorbed by ~he foamable particles removed after a 3 hour impregnation was measured to be 407 parts by weigh~.
Foaming properties of the f~amable particles with the passage of time and state of cells were examined in the same manner as in Example 1.
Table 3 Standing Expansion State of Presence of Time_ Multiple Cells cores Immediately after re- 34 (30 sec) good no cores moval 2 hrs 30 (30 sec) good no cores
Upon this addition, the rotary vessel and the resin were maintained at 35C and the adding rate was adjusted so that the total amount of the mlxture could be added in three hours.
The amount of the mixture solution absorbed by ~he foamable particles removed after a 3 hour impregnation was measured to be 407 parts by weigh~.
Foaming properties of the f~amable particles with the passage of time and state of cells were examined in the same manner as in Example 1.
Table 3 Standing Expansion State of Presence of Time_ Multiple Cells cores Immediately after re- 34 (30 sec) good no cores moval 2 hrs 30 (30 sec) good no cores
4 hrs 31 (60 sec) good no cores 12 hrs 26 (60 sec) good no cores Example 4 The same impregnation procedure as described in Example 3 was conducted using 3,000 parts by weight of poly olefin particles composed of 30 % by weight of polyethylene nd 70 % by weight of styrene monomer and a mix~ure of 300 parts by weight of pentane and 55 parts by weight of xylene~
(13) 1 The rate of adding the mix~ure solution dropwise was adjusted so that the rnixture solution could be added in 2 hours while keeping the impregnation temperature of 60C~
After completion of the dropwise addition, tile resulting product was rotated for further 1 hour while keeping the temperature at 60C, then cooled to ordinary temperatures, followed by removing foamable particles out of the rotary vessel. The particles were evaluated in the same manner as in Example 3. The amount of the mixture absorbed by ~he foam^-able particles was measured to be 340 parts by weight immedîately after removal.
Table 4 Standing Expansion State of Presence of Time Multiple Cells Cores _ _ Immediately after 46 (30 sec)good no cores removal 2 hrs 43 (30 sec)good no cores 4 hrs ~7 (45 sec)good no cores 12 hrs 41 (60 sec)good no cores Example 5 400 Parts by weight of the polyolefin particles used in Example 1 was placed in a double-cone tumbler having an internal volume of 850 liters and being resistant against a pressure of 10 kg/cm2. 38 Parts by weight of n-butane and 10 parts by weight of toluene were added to the vessel all at once while rotating the tumbler at 18 rpm. Thereafter, the insi.de : temperature was raised to 50C in about 1 hour, and was ~hen kept at 50C for further one hour, followed by cooling with (14) 1 18C well water. After cooling, ~he foamable particles were removed and evaluated in the same manner as in Example ~l~
The amount of the mixture absorbed by the foamable particles was measured to be parts by weight immediately after ~he removal.
Table 5 StandingExpansion State of Presence of Time Multiple Cells Cores Immediately lO after 60 (15 sec)good no cores removal 2 hrs 40 (45 sec)good no cores 4 hrs 35 (60 sec)good no cores 12 hrs lO (60 sec)good no cores Example 6 400 Parts by weight of the polyolefin particles used in Example l were placed in a double-cone tumbler having an internal volume of 850 liters and being resistant against a pressure of 10 kg/cm2. 0.08 Parts by weight of an anthra~
quinone green dye (trade name: Diaresin Fast Brill. Green 5G;
made by Mitsubishi Chemical Industries, Ltd.) was added thereto while rotating the tumbler at 18 rpm. The rotation was further continued for 10 minutes. Then, 38 parts by weight of n-butane and 10 parts by weight of toluene weré added there~o all at once, and the inside temperature was raised to 55C
in about 1 hour. The rotation was maintained for an additiol~al hour while maintaining the temperature at 55C, followed by cooling with 18C well water and removing the foamable par~icles out of the tumbler. Thus, colored foamable particles were (15) l obtained. The resulting colored foamable particles were uniformly colored and had quite the same fluidlty as that obtained in Example 5, and were ~herefor easy to handle. Further9 when the colored foamable particles were pressed onto whi.te paper by a finger, the white paper was not colored. Therefore, it is apparent that the dye was not on the surface of the parti-cles but was uniformly impregnated therein.
The amount of mixture absorbed by the colored foarnab~le particles immediately after removal and evaluation of ~he particles according to Example 1 were conducted in the same manner as with the foamable particles of Example 5.
Additionally, colored foamable particles were similarly obtained using an acenaphthene yellow dye (trade name: Diaresin Yellow F; made by Mitsubishi Chemical Industries, Ltd.) or an azo red dye (trade name: Diaresin Red H; made by Mitsubishi Chemical Industries, Ltd.) in place of the anthra~uinone green dye. These dyes were similarly uniformly impregnated in the particles.
Com~arative Example 1 1,500 Parts by weight of the polyolefin resin partlcles in Example 1 was placed in a cylindrical vessel (250 mm x 180 ~ ,nm) containing no screen. Then, an emulsion dispersion previously prepared from 30 parts by weight of toluene, 0.5 pàrts by weigh~
of an emulsifier (sodium dodecylbenzenesulfonate), and 2,000 parts by weight of water was added thereto ~o prepare a suspen--sion. Subsequently, 225 parts by weight of pentane was added thereto, and the resulting mixture was stirred for 4 hours at 50C to effect impregnation. The thus-obtained foamable particles were removed and dehydrated.
(16) ~ , l Foams were prepared from the particles after allowing to stand for a given time to examine the foaming properties and the state of cells, in the same manner as Example 1 Table 6 Standing Expansion State of Pr~sence or Time Multi~le Core Absence of Core Immediately after removal 30 (30 sec)bad present 2 hrs 22 (60 sec) bad absent 4 hrs 15 (60 sec) bad absent 12 hrs 7 (60 sec) bas absent As is seen from the above results, the foamable particles obtained by the present invention have a good state of cell, or in other words, have uniform and fine foamed cells with a definite shape. The cells of the foamable particles obtained by the present invention do not change with the passage of time and always provide moldable cells. In addition, with respect to foaming properties, the foamable particles obtained by the process of the present invention do not undergo a serious decrease in expansion multiple, even when allowed to stand for a long period of time, and therefore, keep their excellent foama-bility.
On the other hand, under very similar conditions, foamable particles, which are obtained in a process using a liquid-phase impregnation (or dipping method), absorb ~he blowing agent and a solvent in such excessive amounts tha~
foamed particles obtained by heating these foamable particles are extremely easily contracted and contain cells too coarse to mold.
(17) l Foamable particles obtained by suspension impregna~lon are also found to form coarse cells and undergo reduction in foamability with the passage of time.
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one ski.lled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.
(18)
(13) 1 The rate of adding the mix~ure solution dropwise was adjusted so that the rnixture solution could be added in 2 hours while keeping the impregnation temperature of 60C~
After completion of the dropwise addition, tile resulting product was rotated for further 1 hour while keeping the temperature at 60C, then cooled to ordinary temperatures, followed by removing foamable particles out of the rotary vessel. The particles were evaluated in the same manner as in Example 3. The amount of the mixture absorbed by ~he foam^-able particles was measured to be 340 parts by weight immedîately after removal.
Table 4 Standing Expansion State of Presence of Time Multiple Cells Cores _ _ Immediately after 46 (30 sec)good no cores removal 2 hrs 43 (30 sec)good no cores 4 hrs ~7 (45 sec)good no cores 12 hrs 41 (60 sec)good no cores Example 5 400 Parts by weight of the polyolefin particles used in Example 1 was placed in a double-cone tumbler having an internal volume of 850 liters and being resistant against a pressure of 10 kg/cm2. 38 Parts by weight of n-butane and 10 parts by weight of toluene were added to the vessel all at once while rotating the tumbler at 18 rpm. Thereafter, the insi.de : temperature was raised to 50C in about 1 hour, and was ~hen kept at 50C for further one hour, followed by cooling with (14) 1 18C well water. After cooling, ~he foamable particles were removed and evaluated in the same manner as in Example ~l~
The amount of the mixture absorbed by the foamable particles was measured to be parts by weight immediately after ~he removal.
Table 5 StandingExpansion State of Presence of Time Multiple Cells Cores Immediately lO after 60 (15 sec)good no cores removal 2 hrs 40 (45 sec)good no cores 4 hrs 35 (60 sec)good no cores 12 hrs lO (60 sec)good no cores Example 6 400 Parts by weight of the polyolefin particles used in Example l were placed in a double-cone tumbler having an internal volume of 850 liters and being resistant against a pressure of 10 kg/cm2. 0.08 Parts by weight of an anthra~
quinone green dye (trade name: Diaresin Fast Brill. Green 5G;
made by Mitsubishi Chemical Industries, Ltd.) was added thereto while rotating the tumbler at 18 rpm. The rotation was further continued for 10 minutes. Then, 38 parts by weight of n-butane and 10 parts by weight of toluene weré added there~o all at once, and the inside temperature was raised to 55C
in about 1 hour. The rotation was maintained for an additiol~al hour while maintaining the temperature at 55C, followed by cooling with 18C well water and removing the foamable par~icles out of the tumbler. Thus, colored foamable particles were (15) l obtained. The resulting colored foamable particles were uniformly colored and had quite the same fluidlty as that obtained in Example 5, and were ~herefor easy to handle. Further9 when the colored foamable particles were pressed onto whi.te paper by a finger, the white paper was not colored. Therefore, it is apparent that the dye was not on the surface of the parti-cles but was uniformly impregnated therein.
The amount of mixture absorbed by the colored foarnab~le particles immediately after removal and evaluation of ~he particles according to Example 1 were conducted in the same manner as with the foamable particles of Example 5.
Additionally, colored foamable particles were similarly obtained using an acenaphthene yellow dye (trade name: Diaresin Yellow F; made by Mitsubishi Chemical Industries, Ltd.) or an azo red dye (trade name: Diaresin Red H; made by Mitsubishi Chemical Industries, Ltd.) in place of the anthra~uinone green dye. These dyes were similarly uniformly impregnated in the particles.
Com~arative Example 1 1,500 Parts by weight of the polyolefin resin partlcles in Example 1 was placed in a cylindrical vessel (250 mm x 180 ~ ,nm) containing no screen. Then, an emulsion dispersion previously prepared from 30 parts by weight of toluene, 0.5 pàrts by weigh~
of an emulsifier (sodium dodecylbenzenesulfonate), and 2,000 parts by weight of water was added thereto ~o prepare a suspen--sion. Subsequently, 225 parts by weight of pentane was added thereto, and the resulting mixture was stirred for 4 hours at 50C to effect impregnation. The thus-obtained foamable particles were removed and dehydrated.
(16) ~ , l Foams were prepared from the particles after allowing to stand for a given time to examine the foaming properties and the state of cells, in the same manner as Example 1 Table 6 Standing Expansion State of Pr~sence or Time Multi~le Core Absence of Core Immediately after removal 30 (30 sec)bad present 2 hrs 22 (60 sec) bad absent 4 hrs 15 (60 sec) bad absent 12 hrs 7 (60 sec) bas absent As is seen from the above results, the foamable particles obtained by the present invention have a good state of cell, or in other words, have uniform and fine foamed cells with a definite shape. The cells of the foamable particles obtained by the present invention do not change with the passage of time and always provide moldable cells. In addition, with respect to foaming properties, the foamable particles obtained by the process of the present invention do not undergo a serious decrease in expansion multiple, even when allowed to stand for a long period of time, and therefore, keep their excellent foama-bility.
On the other hand, under very similar conditions, foamable particles, which are obtained in a process using a liquid-phase impregnation (or dipping method), absorb ~he blowing agent and a solvent in such excessive amounts tha~
foamed particles obtained by heating these foamable particles are extremely easily contracted and contain cells too coarse to mold.
(17) l Foamable particles obtained by suspension impregna~lon are also found to form coarse cells and undergo reduction in foamability with the passage of time.
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one ski.lled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.
(18)
Claims (6)
1 A process for producing foamable polyolefin particles which comprises adding a mixture of 3 to 15 parts by weight of a blowing agent and 0.5 to 5 parts by weight of a blowing aid to 100 parts by weight of polyolefin particles in a fluid state, the particles comprising polyolefin resin with vinylaromatic resin chemically bonded thereto, wherein the adding is conducted under substantially anhydrous conditions so that the blowing agent is present in the particles in a gas phase and not a liquid phase.
2 The process as described in claim 1, wherein the polyolefin particles are prepared by polymerizing 20 to 70 wt % of polyolefin resin and 80 to 30 wt % of vinylaromatic monomer in an aqueous medium.
3. The process as described in claim 1, wherein said polyolefin resin is an ethylene homopolymer or copolymer resin.
4. The process as described in claim 1, wherein said vinylaromatic resin is polystyrene.
5. The process as described in claim 1, wherein the mixture of blowing agent and the blowing aid and polyolefin particles are maintained at a temperature from ordinary temperature to 70°C
during the adding step.
during the adding step.
6. A process for producing foamable polyolefin particles which comprises the steps of:
adding to a vessel, 100 parts by weight of polyolefin particles comprising polyolefin resin with vinylaromatic resin chemically bonded thereto, moving the polyolefin particles in a manner so that the polyolefin particles are in a fluid state (19) contacting the polyolefin particles while maintaining the fluid state with an anhydrous mixture of 3 to 15 parts by weight of a blowing agent and 0.5 to 5 parts by weight of a blowing aid, thereby providing foamable polyolefin particles consisting of the polyolefin particles and the mixture, the mixture being in a gas phase.
(20)
adding to a vessel, 100 parts by weight of polyolefin particles comprising polyolefin resin with vinylaromatic resin chemically bonded thereto, moving the polyolefin particles in a manner so that the polyolefin particles are in a fluid state (19) contacting the polyolefin particles while maintaining the fluid state with an anhydrous mixture of 3 to 15 parts by weight of a blowing agent and 0.5 to 5 parts by weight of a blowing aid, thereby providing foamable polyolefin particles consisting of the polyolefin particles and the mixture, the mixture being in a gas phase.
(20)
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP82168/82 | 1982-05-14 | ||
| JP57082168A JPS58198541A (en) | 1982-05-14 | 1982-05-14 | Production of expandable particle |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1181550A true CA1181550A (en) | 1985-01-22 |
Family
ID=13766897
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000428154A Expired CA1181550A (en) | 1982-05-14 | 1983-05-13 | Process for producing foamable polyolefin particles |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US4429059A (en) |
| JP (1) | JPS58198541A (en) |
| KR (1) | KR920001625B1 (en) |
| AU (1) | AU550143B2 (en) |
| CA (1) | CA1181550A (en) |
| DE (1) | DE3317557A1 (en) |
| FR (1) | FR2526802B1 (en) |
| GB (1) | GB2121046B (en) |
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| US4695593A (en) * | 1986-02-21 | 1987-09-22 | Japane Styrene Paper Corporation | Prefoamed propylene polymer-base particles, expansion-molded article produced from said particles and production process of said article |
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| US10006177B2 (en) | 2015-09-23 | 2018-06-26 | Nova Chemicals Inc. | Workstation for flagman |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3126354A (en) * | 1964-03-24 | Method of impregnating polystyrene | ||
| FR1291425A (en) * | 1960-06-09 | 1962-04-20 | Basf Ag | Process for the production of expandable thermoplastics |
| US3743611A (en) | 1966-06-08 | 1973-07-03 | Hitachi Ltd | Foamable thermoplastic beads and a process for the preparation thereof |
| GB1383924A (en) * | 1971-03-25 | 1974-02-12 | Kanegafuchi Chemical Ind | Method of manufacturing polymer particles having uniform crosslin king and expanded shaped articles formed therefrom |
| FR2255314A1 (en) * | 1973-12-20 | 1975-07-18 | Sekisui Plastics | Expandable polyethylene particles prodn. - by polymn. of mixture contg. major proportion of styrene monomers |
| US4168353A (en) * | 1976-04-21 | 1979-09-18 | Sekisui Kaseihin Kogyo Kabushiki Kaisha | Process for producing foamable polyethylene resin particles |
| US4303756A (en) | 1978-10-16 | 1981-12-01 | Sekisui Kaseihin Kogyo Kabushiki Kaisha | Process for producing expandable thermoplastic resin beads |
-
1982
- 1982-05-14 JP JP57082168A patent/JPS58198541A/en active Granted
-
1983
- 1983-05-13 DE DE19833317557 patent/DE3317557A1/en active Granted
- 1983-05-13 CA CA000428154A patent/CA1181550A/en not_active Expired
- 1983-05-13 FR FR8308002A patent/FR2526802B1/en not_active Expired
- 1983-05-14 KR KR1019830002144A patent/KR920001625B1/en not_active IP Right Cessation
- 1983-05-16 US US06/495,108 patent/US4429059A/en not_active Expired - Lifetime
- 1983-05-16 AU AU14556/83A patent/AU550143B2/en not_active Ceased
- 1983-05-16 GB GB08313401A patent/GB2121046B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB2121046B (en) | 1985-07-31 |
| AU1455683A (en) | 1983-11-17 |
| FR2526802B1 (en) | 1987-04-30 |
| GB8313401D0 (en) | 1983-06-22 |
| JPH0249331B2 (en) | 1990-10-29 |
| JPS58198541A (en) | 1983-11-18 |
| GB2121046A (en) | 1983-12-14 |
| AU550143B2 (en) | 1986-03-06 |
| FR2526802A1 (en) | 1983-11-18 |
| KR840004918A (en) | 1984-10-31 |
| DE3317557C2 (en) | 1990-12-06 |
| KR920001625B1 (en) | 1992-02-21 |
| DE3317557A1 (en) | 1983-11-17 |
| US4429059A (en) | 1984-01-31 |
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